Recently, by-wire systems for vehicles have been widely developed. By-wire systems transmit electrical signals through wire to perform specific operations, instead of using mechanical systems to directly transmit mechanical driving energy. Such by-wire system includes a brake-by-wire system, a steer-by-wire-system, and the like.
Recently, shift-by-wire systems that perform gear shifting by an electrical signal have been under development. In a shift-by-wire system, various shift links for connecting a shift lever and a transmission have been substituted by a wire transmitting an electrical signal, so that more efficient use of a passenger compartment is possible and weight of a vehicle can be substantially decreased.
Prior shift-by-wire systems eliminated shift links of an automatic transmission such as a lever, an inhibitor switch, and a manual valve, and utilized an electronic solenoid to perform gear shifting. Therefore, prior shift-by-wire systems had a drawback in that the overall structure of a transmission must be changed.
Furthermore, the prior shift-by-wire system passively copes with system failure, i.e., it provides only a fail-safe function (e.g., a restriction of a position of a shift lever during a shift error). That is, prior shift-by-wire systems have few strategies for coping with a system failure.
The information disclosed in this Background of the Invention section is only for enhancement of understanding of the background of the invention, and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art that is already known to a person skilled in the art.